There are presently known many solutions of capsules meant for use in beverage extraction machines, such as espresso coffee, including of the pod type, provided in a substantially air un-tight material, and of the capsule type, provided in substantially airtight materials. The opening of such kind of recipients, for passage of the extraction flow, raises several questions from the technical point of view, both in terms of the control upon the moments of entry and exit (and, therefore, of the flow residence period in its interior) as well as in terms of the configuration of the section of flow passage (format, dimension, distribution) for the entry and for the exit of said pressurized fluid flow. In fact, these parameters have a substantial influence upon the final quality of the beverage obtained and, in general, vary according to the type of aromatic substance being used. Moreover, it is further important to consider the set of forces required by an extraction device, notably in a respective extraction chamber, to carry out said opening of entry and exit of the capsule, as well as an eventual variation of the latter for different types of substances being used.
The solution usually practiced for the opening of the capsule relates to a certain form of rupture of a certain material used in a construction element in a certain zone of the capsule, usually as a result of the application of a certain mechanical force. Moreover, one frequently tries to use the hydraulic force generated inside the capsule by the pressurized fluid flow, to also actuate, at least in part, the exit out of it.
Document EP 1975087 presents a capsule including a tubular element disposed inside and participating in the distribution of the pressurized fluid flow, from the entry in the capsule to the exit therefrom. Also in this case the opening of the flow entry and exit is carried out by means of perforating the construction material in respective zones. Moreover, in this case, the tubular element is not actuated so as to carry out any displacement. The tubular element provides, in a passive manner, an assisting function to the flow distribution inside the capsule, but does not carry out any flow actuation function.